We also did an experiment with this: http://imgur.com/tdnympM http://imgur.com/tdnympM The same problem existed. So it is not inertia in this case. However, in

We also did an experiment with this: http://imgur.com/tdnympM http://imgur.com/tdnympM The same problem existed. So it is not inertia in this case. However, inertia could also interfere with the gravity vector.